An application interface is the means by which a user interacts with one or more devices comprising a system application (a.k.a. “application”) in order to enable effective operation and control of the application by the user. Typically an application interface comprises both hardware and software components to provide both a means of input (allowing a user to manipulate the application) and a means of output (allowing the application to indicate the effects of the users' manipulation). The outputs from the application interface provide feedback and/or deliver information from the application to the user which in turn aids the user in making operational decisions. The objective of any new application interface is to improve the operation of an application in a way which produces improved or enhanced results for the user, and generally the more meaningful improvements to application interfaces are those that reduce the user's input while achieving the same or better desired outputs while simultaneously minimizing undesired outputs.
Separately, a substantial amount of useful information can be derived from determining the direction a user is looking at different points in time. Indeed, a vast amount of gaze tracking research using any of several vision-based approaches (i.e., tracking user eyes by any of several existing means) is already being undertaken in several different contexts for several different potential uses. However, understanding a user's gazing direction only provides semantic information on one dimension of the user's interest and does not take into account contextual information that is mostly given by speech and other audible (and/or visual) means of communications. In other words, the combination of gaze tracking coupled with speech tracking provides richer and more meaningful information about the user than the simpler forms of information currently being utilized today.